Simulation of Hydraulic Structures in 2D High-Resolution Urban Flood Modelling

Urban flooding as a result of rapid catchment respond to intense rainfall, failure of flood defences, etc. is usually featured with highly transient hydrodynamics. Reliable and efficient prediction and forecasting of these urban flash floods is still a great technical challenge. Meanwhile, in the urban environments, the development of a flood event may be predominantly influenced by flow-regulating and flood-protection hydraulic infrastructure systems such as dams, sluice gates and pump stations, which should be effectively taken into account in an urban flood model. However, direct simulation of hydraulic structures is not a current practice in 2D urban flood modelling. This work aims to develop a robust numerical approach to directly simulate the effects of gate and wall structures in a 2D high-resolution urban flood model. The resulting modelling tool allows us to efficiently evaluate the influence of certain key hydraulic infrastructure during an urban flood event.

The adopted urban flood simulation model solves the full 2D shallow water equations using a finite volume Godunov-type shock-capturing numerical scheme, incorporating an HLLC approximate Riemann solver. The model is accelerated using multiple graphics processing units (GPUs) to enable computationally efficient large-scale urban flood modelling at high resolutions (e.g. ~2m spatial resolution across a city of ~1000 km²). New computational module is developed and fully coupled to the 2D model to directly simulate the highly transient flood waves through hydraulic structures. Different coupling approaches, e.g. flux and source term coupling, are implemented and compared. The enhanced urban flood modelling tool is tested by reproducing the laboratory experiments of flood routing in a flume with partially open sluice gates conducted in the hydraulic laboratory at the Zhejiang Institute of Hydraulics and Estuary, China. Numerical results are compared favorably with experimental measurements (e.g. Figure 1). Satisfactory results demonstrate that the present modelling approach is able to accurately simulate the flow through hydraulic structures and enhance the predictive capability of the 2D model for urban flood modelling.